When air pressure changes in a semiconductor exposure apparatus, an aberration which is an optical characteristic error is generated. A correction method of an aberration caused by a daily moderate change in air pressure is disclosed in, e.g., Japanese Patent Application Laid-Open No. 8-305034. According to Japanese Patent Application Laid-Open No. 8-305034, a projection optical system mainly configured with a single glass material measures air pressure for each wafer and corrects an aberration by changing the wavelength of an exposure light source in accordance with the change in air pressure, and to correct a magnification difference between processes, drives a projection lens in the optical-axis direction, thereby performing projection magnification correction.
Along with further miniaturization of patterns for the recent semiconductor integrated circuits, such as an IC or LSI, higher precision of image forming characteristics in exposure is required. For this reason, even a slight change in air pressure is difficult to tolerate. For instance, Japanese Patent Application Laid-Open No. 2001-085292 discloses a correction method of an aberration caused by a slight but sudden change in air pressure due to human factors or the like under the environment where an exposure apparatus is installed. According to Japanese Patent Application Laid-Open No. 2001-085292, since there is a case that opening and closing of a door to a clean room causes a change in the air pressure of approximately 0.5 hPa/sec, the change in air pressure is detected by a barometer employing a responsive laser interferometer, and a projection lens is driven in an optical-axis direction to correct an aberration caused by the detected change in air pressure, or a wavelength of the exposure light source is changed to correct an aberration caused by the detected change in air pressure.
In general, an aberration caused by a change in air pressure is extremely large in the projection magnification and focus, thus requiring reduction by correction. On the contrary, aberrations such as distortion, spherical aberration, coma, astigmatism, curvature of field and the like are relatively small so that they do not create problems in terms of exposure characteristics.
However, aforementioned Japanese Patent Application Laid-Open No. 8-305034 does not include means for correcting an aberration caused by a change in air pressure during an exposure. Further, it does not take aberration correction means into consideration for a case where the projection optical system is not configured with a single glass material. Moreover, in the aforementioned Japanese Patent Application Laid-Open No. 2001-085292 which discloses a correction method using a barometer that employs a responsive laser interferometer, there is a possibility that accurate aberration correction cannot be performed because a barometer employing a laser interferometer generates an air pressure error due to changes in environmental conditions of temperature and humidity.